Means for clearing short circuits in electrical precipitators



y 6, 1965 H. KLEMPERER 3,192,638

MEANS FOR CLEARING SHORT CIRCUITS IN ELECTRICAL PRECIPITATORS Filed Jan. 10, 1964 A am' AVzmperer United States Patent MEANS FGR CLEARING SHORT CIRCUITS DJ ELECTRICAL PRECHITATORS Hans Klemperer, Belmont, Mass, assignor to Refractory & Insulation Corporation, New York, N.Y.,.a corporation of Delaware Filed Jan. 10, 1964, 'Ser. No. 336,937

3 Claims. (Cl. 55-139) The present invention relates to electrostatic precipitators and this application is a continuation-in-part of my copending application Serial No. 67,557 filed November 7, 1960, which has now matured into Patent No. 3,149,- 938 granted September 22, 1964.

The primary object of this invention is to provide a novel circuit arrangement for a precipitator that selectively permits the removal of electrodes having short circuits or low voltage arc-overs between the electrodes and grounded collecting surfaces without necessitating a complete shut-down of the precipitator.

The precipitator in which the invention is embodied effects removal of particulate matter from a flowing column of impure gases by electrostatic means. A precipitator of this type may comprise a plurality of sections, each section being connected to an individual power supply and each section comprising a multitude of grounded collecting elements or tubes in combination with discharge electrodes connected to a high voltage source adapted to ionize a stream of particle-laden gases flowing through the electrode arrangement such that the particulate matter carried by the gases is collected on the grounded tubes.

During operation of such apparatus, the ionizing electrodes or their supporting insulators may develop defects that cause short circuits to ground or flashovers before operating voltages are reached to the effect that the collecting efliciency of the entire bank of electrodes with which they are associated is substantially reduced.

The present invention contemplates the provision of apparatus of the kind described in which one or a number of short circuited electrodes in an electrostatic precipitator may be electrically separated from the system without affecting the operation of the system or necessitating a shut-down of the precipitator for purposes of repair.

The invention may be described generally as the application of a power feed to a number of fused electrodes in combination with fuse evaporating means that in case of a fault in any electrode may effectively isolate the faulty electrode from the rest of the system.

The invention will be best understood upon consideration of the following detailed description of an illustrative embodiment thereof when read in conjunction with the accompanying drawing in which the single figure represents a schematic view of a gas cleaning system to which is attached a power source and necessary circuitry for fuse evaporation which evaporates fuses of electrodes that are substantially shorted to ground.

The drawing illustrates a section of an electrostatic precipitator including a bank of grounded collecting electrodes or tubes having discharge electrodes 12 supported by insulators 14. The electrodes are connected to a power supply 15 by a cable 16 having a grounded sheath 18. Fuses 24 connect the high voltage lead 25 to each electrode or group of electrodes as desired to provide means to disconnect electrically from the power supply any electrode that has developed a ground connection or which flashes over to ground before reaching sufficiently high voltage as required for normal ionization.

To this precipitating equipment there is connected by means of moving switch 21 to a down position, fuse blowing apparatus that comprises a capacitor 22 which is 3,192,688 Patented July 6, 1965 ice grounded at one end and connected serially at the other end to an inductance 26. A two-way switch 32 in the fuse blowing apparatus connects the power supply 15 to the capacitor 22 when in a down position, and when raised to an up position by the selective actuation of push button 34, the charged condenser 22 is discharged to the bank of collecting tubes through the interconnecting shielded cable 16.

Apparatus of this type is designed to evaporate the particular fuse which leads to any shorted electrode or one that arcs over at a voltage below its normal operating voltage. The continuing occurrence of an arc-over below normal operating voltage in a precipitator indicates the presence of a faulty electrode. To disconnect this faulty electrode from the bank of operating electrodes, the fuse blowing apparatus 22 and 26 is connected to the power line leading thereto by moving switch 21 to a down position while the switch 32 is also in a normal down position. The manual voltage control 28 is raised to charge the capacitor 22 and when it is charged to a predetermined level sufficient to blow a fuse 24, the push button 34 is closed to actuate the solenoid 35 and raise the switch 32 to its up position. With switch 32 raised, the charge on the capacitor is discharged into the precipitator, and at the moment the arc-over occurs between the faulty electrode and the ground the energy stored in the capacitor 22 discharges through the arc-over path and evaporates the fuse connected thereto. After the fuse has been blown or evaporated, the fuse blowing equipment is disconnected from the system by permitting switch 32 to return to its down position while switch 21 is raised to its up position to again connect the bank of collecting tubes to the power supply 15 in order that normal operation may he resumed.

The energy stored in the capacitor battery must be large enough to evaporate the fuse upon discharge. The fuse on the other hand must be capable of withstanding all current that flows to the fused electrode or group of electrodes during normal operation. Good results are obtained by using a capacity of 20 micro-farads with faulty electrodes that are over above 6 kv. The discharge of the stored energy is slowed down by means of the inductance 26 which is in the order of millihenries, in order to avoid damage to circuit elements.

Stainless steel wire has been used successfully for fuses which are designed to burn out at sustained current loads of about 10 amperes. The ordinary operating current passing a fuse leading to, for instance, 10 electrodes is between 10 and 20 milliamperes, and in case of individually fused electrodes it is between 1 and 2 milliamperes. The current peak during operational flashovers in the precipitator is limited to from 2 to 5 amperes by the design of the power supply. This leaves the fuse unaffected during ordinary operation of the precipitator while it evaporates instantly upon application of the aforesaid capacitor discharge.

1 claim:

1. In an electrostatic precipitator having a bank of electrodes, a power lead connected to each electrode, fuse means intermediate said electrodes and said power lead, a power supply, means for blowing any of said fuses which are connected to a faulty electrode having a low voltage arc-over, said means comprising a capacitor, switch means operable to selectively connect said power supply to the capacitor or to the precipitator, and other switch means operable to discharge said capacitor through the faulty electrode to blow the fuse leading thereto.

2. In an electrostatic precipitator having a bank of electrodes, a power lead connected to each electrode, fuse means intermediate said bank of electrodes and said power lead, a power supply, means for blowing any of said fuses 3 which are connected to a faulty electrode having a low voltage arc-over, said means comprising a capacitor, switch means operable to alternately connect said power supply to the capacitor or the precipitator, and other switch means operable to alternately connect said capacitor to the power supply or the precipitator.

3. In an electrostatic precipitator having a bank of electrodes and a power supply, a power lead connecting the precipitator to the power supply, fuse means intermediate each of said electrodes and the power lead, means for blowing a fuse leading to a faulty electrode causing a low voltage arc-over comprising a capacitor, switch means operable to connect the power supply to the ca pacitor in one position and the power supply to the precipitator in a second position, and a second switch means References Cited by the Examiner UNITED STATES PATENTS 1,455,781 5/23 Dubilier 3l7-261 2,053,445 9/36 Rose. 2,979,158 4/61 Ulier 55l39 HARRY B. THORNTON, Primary Examiner. 

1. IN AN ELECTROSTATIC PRECIPITATOR HAVING A BANK OF ELECTRODES, A POWER LEAD CONNECTED TO EACH ELECTRODE, FUSE MEANS INTERMEDIATE SAID ELECTRODES AND SAID POWER LEAD, A POWER SUPPLY, MEANS FOR BLOWING ANY OF SAID FUSES WHICH ARE CONNECTED TO A FAULTY ELECTRODE HAVING A LOW VOLTAGE ARC-OVER, SAID MEANS COMPRISING A CAPACITOR, SWITCH MEANS OPERABLE TO SELECTIVELY CONNECT SAID POWER SUPPLY TO THE CAPAITOR OR THE PRECIPITATOR, AND OTHER SWITCH MEANS OPERABLE TO DISCHARGE SAID CAPACITOR THROUGH THE FAULTY ELECTRODE TO BLOW THE FUSE LEADING THERETO. 